It is “solid evidence that tyrannosaurs drastically changed their diet as they grew up,” said Dr Darla Zelenitsky, from the University of Calgary.

“We now know that these teenage [tyrannosaurs] hunted small, young dinosaurs,” said Dr Zelenitsky, one of the lead scientists in this study, which is published in the journal Science Advances.

But, Dr Zelenitsky, added, “these smaller, immature tyrannosaurs were probably not ready to jump into a group of horned dinosaurs, where the adults weighed thousands of kilograms”.

Staff at Alberta’s Royal Tyrell Museum of Palaeontology eventually noticed small toe-bones sticking out from the ribcage.

“The rock within the ribcage was removed to expose what was hidden inside,” explained Dr Therrien, who is the other lead scientist in this study.

While the adults bit and scraped with their powerful “killer banana” teeth, “this animal was selecting and even dissecting its prey - biting off the legs and swallowing them whole”.

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